1. Field of the Invention
The present invention relates to a method for producing 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride, which is an important starting material for preparing a radiation-sensitive positive photoresist composition, a photosensitive component of a positive photosensitive lithographic printing master plate, etc.
2. Background Art
1,2-Naphthoquinone-2-diazide-4-sulfonyl chloride has a chemical structure represented by the following formula (1). This compound has a melting point of 146-148.degree. C. (decomposition). In "Chemical Abstracts," an abstract journal issued by the American Chemical Society, this compound is called 3-diazo-3,4-dihydro-4-oxo-1-naphthalenesulfonyl chloride, and the CAS registry number of the compound is "36451-09-9." ##STR1##
Methods for producing 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride are divided into the following two types, (a) and (b), on the basis of the sequence of steps. Methods of type (a) are industrially employed at the present time. However, since methods of this type are not necessarily directly related to the method of the present invention, they will be briefly described only in outline form. Methods of type (b) are not industrially employed at the present time. However, since the method of the present invention is categorized under method (b), essential points of a typical known method categorized under method (b) will be described.
Methods of type (a) are drawn to a process in which sodium 1,2-naphthoquinone-2-diazide-4-sulfonate (CAS registry number: 64173-96-2) is synthesized (first step) and then converted to a compound of the above-described formula (1) (second step) (see, for example, DRP171024, DRP175593, German Patent Nos. 246573 and 246574, Japanese Patent Application Laid-Open (kokai) No. 196860/1984, and Japanese Patent Application Laid-Open (kokai) No. 27098/1996). According to such a method, many difficulties are encountered in the first step; i.e., in the synthesis of the compound of CAS registry number 64173-96-2. Particularly, synthesis of this compound is carried out by diazotization of sodium 3-amino-4-hydroxynaphthalene-1-sulfonate in the presence of a salt of a heavy metal such as copper, and therefore, the product is contaminated with a heavy metal salt. Thus, in order to make the compound usable as a photosensitizer for use in photoresist, the heavy metals must be eliminated. Practicing the elimination process for heavy metals on an industrial scale is considerably burdensome, and hence demand remains for a more effective method for producing the compound of formula (1).
Methods of type (b) are drawn to a process in which 1,2-naphthoquinone-2-diazide is treated with chlorosulfuric acid and thionyl chloride, to thereby yield the compound represented by formula (1). The method of the present invention is a method of this type. According to "Chemical Abstracts," 1,2-naphthoquinone-2-diazide is named 2-diazo-1(2H)-naphthalenone, and the CAS registry number of the compound is 879-15-2. The compound has a chemical structure represented by the following formula (2). ##STR2##
Methods of type (b) are industrially promising, but thus far there have been disclosed very few study examples thereof. The main reason is failure to establish effective methods for producing the compound represented by the above-described formula (2). The present inventors previously invented a significantly effective method for producing the compound described below (Japanese Patent Application No. 166744/1998). They continued studies on methods of type (b) in great detail, to thereby complete the present invention.
Very few published documents mention methods of type (b). E. Sauer et al. disclose a method in which 1,2-naphthoquinone-2-diazide is reacted with chlorosulfuric acid at 63.degree. C. for 80 minutes, to thereby obtain a mixture of a sulfonated compound and a chlorosulfonated compound of the diazide. In this method, the theoretical yields of 1,2-naphthoquinone-2-diazide-4-sulfonic acid and 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride are about 45% and about 50% respectively (J. Prakt. Chem. 333, 467 (1991)). B. I. Below et al. disclose a method in which 1,2-naphthoquinone-2-diazide is reacted in chlorosulfuric acid (14.3 times (by mol) the amount of the diazide) at 70.degree. C. for two hours to thereby obtain crystals having a melting point of 138-139.degree. C., and 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride is obtained at a yield of 70% (U.S.S.R Pat. 173,756 (1964)). However, judging from the melting point of the crystals and the results of an experiment conducted by E. Sauer et al., the crystals are believed to be a mixture of the compound represented by formula (1), which serves as a main component, and 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride. In addition, Wolter, Gerhard, et al. disclose a method in which 1,2-naphthoquinone-2-diazide is treated with a mixture of chlorosulfuric acid and thionyl chloride, to thereby obtain 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride at a favorable yield (Ger. (East) Pat. DD 269,846 (1989)). The method disclosed by Wolter, Gerhard, et al. is outlined as follows.
A mixture consisting of 6-10 mol of chlorosulfuric acid and 2-5 mol of thionyl chloride based on 1 mol of 1,2-naphthoquinone-2-diazide is cooled, and crystals of 1,2-naphthoquinone-2-diazide are added thereto portionwise. The mixture is reacted at 35-60.degree. C. for 1-3 hours, cooled to room temperature, and poured into a mixture of water and ice. The precipitated crude product is separated and purified through crystallization from acetone at a temperature between -5.degree. C. and -10.degree. C. inclusive. 1,2-Naphthoquinone-2-diazide-4-sulfonyl chloride is described as having a theoretical yield of 70-75%.
The present inventors considered the aforementioned methods of type (b), in which 1,2-naphthoquinone-2-diazide is used as a starting material, to be promising for industrial production of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride, and re-examined a method disclosed in the aforementioned DD 269,846, which is the sole known document mentioning the above method. As a result, the inventors have found that such problems as (1), (2), and (3) described below remain unsolved and that solution of the problems is outstanding.
(1) Problems Involved in Reaction with Thionyl Chloride
In the method disclosed in DD 269,846, 1,2-naphthoquinone-2-diazide is added to a mixture of chlorosulfuric acid and thionyl chloride, and the resultant mixture is allowed to react. However, after studying the method the present inventors have found that the method is unfavorable in the following ways. Crude crystals obtained by treating 1,2-naphthoquinone-2-diazide with a mixture of chlorosulfuric acid and thionyl chloride in accordance with the Example disclosed in DD 269,846 exhibit strong color, the yield of the target compound is poor, and the target compound contains many kinds of impurities. Chlorosulfonation of an aromatic compound making use of a mixture of chlorosulfuric acid and thionyl chloride is generally and widely employed. For example, Blank, Heinz Ulrich discloses a method in which benzene is treated with a mixture of chlorosulfuric acid and thionyl chloride at 50.degree. C. for four hours, to thereby obtain benzenesulfonyl chloride at high purity (Ger. Offen, 2,635,279 (1978)). Sasaki et al. disclose a method in which sodium 1,2-naphthoquinone-2-diazide-4-sulfonic acid is treated with a mixture of chlorosulfuric acid and thionyl chloride at 70.degree. C. for eight hours, to thereby obtain 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride at a yield of 80% (Japanese Patent Application Laid-Open (kokai) No. 27098/1996). Thus, a mixture of chlorosulfuric acid and thionyl chloride is excellent for use as a chlorosulfonation agent for an aromatic compound. However, the present inventors have unexpectedly found that the mixture cannot favorably be applied to 1,2-naphthoquinone-2-diazide. The present inventors have extensively studied the reactivity of 1,2-naphthoquinone-2-diazide and found that, surprisingly, the diazide reacts quite well with thionyl chloride itself at room temperature and produces a mixture of many kinds of species. Also, through analysis by means of liquid chromatography, the mixture produced is identical to impurities other than 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride contained in crystals produced in accordance with the method disclosed in DD 269,846. Furthermore, an experiment carried out by the present inventors clarified that the mixture produced through reaction of 1,2-naphthoquinone-2-diazide with thionyl chloride is thermally unstable and decomposes explosively at about 110.degree. C. Because, as described previously, the target compound, 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride, has a decomposed temperature of 146-148.degree. C. and decomposes explosively at that temperature, the industrial product should not be contaminated with impurities which decompose explosively at 110.degree. C. Accordingly, using a mixture of chlorosulfuric acid and thionyl chloride as a chlorosufoniation agent for 1,2-naphthoquinone-2-diazide is inappropriate, and a new method must be developed.
With regard to a reaction mechanism by which 1,2-naphthoquinone-2-diazide and thionyl chloride react and a mixture containing a variety of species is produced, the present inventors understand the following. Upon application of heat thionyl chloride is known to produce decomposed products of the following formula (3) (P. W. Schenk, H. Tribel, Z. Anorg. Allg. Chem. 229 (1936), 305). EQU 4SOCl.sub.2.fwdarw.S.sub.2 Cl.sub.2 +2SO.sub.2 +3Cl.sub.2 (3)
Also, in the reaction of 1,2-naphthoquinone-2-diazide with thionyl chloride such decomposed products are produced from thionyl chloride. It seems that the decomposed products, particularly chlorine, react with 1,2-naphthoquinone-2-diazide, to thereby produce impurities. In the aforementioned method disclosed by Sasaki et al. (Japanese Patent Application Laid-Open (kokai) No. 27098/1996), 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride is obtained at an excellent yield. The reason for this is understood to be that the sodium 1,2-naphthoquinone-2-diazide-4-sulfonate employed by Sasaki et al. as a starting material does not easily react with the aforementioned decomposed products, such as thionyl chloride.
(2) Problems Regarding Thermal Instability of 1,2-Naphthoquinone-2-diazide
1,2-Naphthoquinone-2-diazide is thermally unstable, and treating a large amount of solid diazide on an industrial scale has been considered dangerous. FIG. 1 shows a DSC (differential scanning calorimetry) curve of 1,2-naphthoquinone-2-diazide crystals(recrystalized from toluene). As shown in FIG. 1, the crystals melt at 77.3.degree. C., begin to decompose at about 95.degree. C., and the exothermic decomposition reaches a peak at 128.2.degree. C. Although 1,2-naphthoquinone-2-diazide is thermally unstable and therefore a dangerous crystalline substance, experiments described in all the disclosed documents mentioning sulfonation or chlorosulfonation of 1,2-naphthoquinone-2-diazide employ solid 1,2-naphthoquinone-2-diazide. Industrial treatment of such a thermally unstable compound in a solid state is unsuitable, and establishment of a safer method for treating the compound is of great interest.
When 1,2-naphthoquinone-2-diazide is prepared in accordance with a method (3) described below, the filtered solid contains water in an amount of 100-150% the target pure product. In order to react 1,2-naphthoquinone-2-diazide with chlorosulforic acid or thionyl chloride water must be completely eliminated. However, elimination of water from a solid substance is difficult, requiring warm air-drying at 40-50.degree. C. for about ten hours and further drying under reduced pressure at 40.degree. C. Also, in such a drying process, solid 1,2-naphthoquinone-2-diazide may thermally decompose, thus involving danger.
(3) Problems in Preparation of 1,2-Naphthoquinone-2-diazide
Three or four documents disclose an experimental method for preparing 1,2-naphthoquinone-2-diazide, which serves as a starting material for 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride, but no suitable method for producing the compound on an industrial scale has yet been disclosed. Patent DD 269,846 recommends the method disclosed in another patent by Wolter, Gerhard, et al. (Ger. (East Germany) DD 221,174 (1984)) as a method for producing 1,2-naphthoquinone-2-diazide which serves as a starting material. However, in this method the yield of 1,2-naphthoquinone-2-diazide from 2-amino-1-naphthalenesulfonic acid is as low as 63%, making this method unsuitable for industrial-scale production.